JP3046319B2 - Stereo improvement and directional servo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a previous patent, US Pat. No. 4,748,669, issued May 3, 1988, for a stereo enhancement system.
1) about. The details described in this document are:
The content disclosed by this earlier patent is used as a reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving stereo sound images, and more particularly, to a method and apparatus used for improving the directionality of left and right channel sounds generated by a stereo speaker system.

2. Description of the prior art A patent for our stereo improvement system, Patent No. 4,747,669 (corresponding Japanese Patent Application No. 62-501080)
Describes a stereo audio image enhancement system, which boosts certain frequency components of the difference signal (bo
ost) and the sum and difference signals are processed to relatively attenuate certain frequency components of the sum signal. Further, the amplitude of the processed difference signal may be controlled by a servo to maintain a relatively constant amount of stereo sound from one record to another, or from one time to another within a given record. (Servo)
Controlled.

In certain applications of the systems and methods of our earlier patents, and many other stereo audio systems, increased directionality of the stereo audio image can be obtained. This increased directionality may be due to the exaggeration or amplification of sound radiating from one or the other side of the stereo sound image or from a region displaced from the center of the sound image, such that sound from one or the other of the superficial sound images may be exaggerated. Means selective enhancement. For example, different audio elements of a sound source, such as a particular instrument, are located at fixed locations relative to one or the other side of the central stage. In reproducing such a sound source, it is desirable to emphasize or augment the fact that individual instruments are located at specific locations, which are displaced from the center of the audio image. With such an enhanced directional environment, not only the individual instruments and the enhanced home position sound sources, but also the movements of the listener's right-to-left or left-to-right moving objects in the acoustic space. Effect is also increased. For example, when watching a high-speed car or airplane moving from right to left on a television or movie screen, not only the vehicle passing through the screen, but also the screen before its visual image appears on the screen. You can hear the vehicle approaching the right side of. At this time, the intensity of the sound from the left is small. Thus, when the vehicle moves to the left edge of the screen and disappears, the sound from the left side of the stereophonic image increases and the sound from the right side decreases. With a vehicle moving from right to left, the sound of the vehicle initially feels to come from the right alone. When the vehicle is on the left side of the screen, the vehicle sounds feel to originate only from the left side of the screen. By appropriately and controllably enlarging the sound that first appears from the right side and the sound that first appears from the left side of the stereophonic image, substantially the entire effect of visually and audibly combined movement from right to left is reduced. , Greatly enhanced. That is, the directionality of the audio image increases. Even in the absence of a visual image, the superficial movement of the auditory image becomes more practical due to the directional enhancement. For moving audio images or laterally displaced fixed sound source elements, such directional enhancements do not exist in any prior art, as far as the applicant is aware.

It is therefore an object of the present invention to provide directional enhancement for stereo audio images.

SUMMARY OF THE INVENTION To achieve the principles of the present invention, according to a preferred embodiment, a stereo difference signal in response to the amplitude of an input signal from one or the other, i.e., from one channel or another channel. Control amplification. More specifically, an amplitude control circuit is provided that has a stereo difference signal as an input and provides an enhanced directional signal as an output.
The amplitude control circuit is controlled by a servo control signal, which is responsive to one of the directional enhanced difference signal and the stereo input signal.

According to another feature of the invention, the directional enhancement signal is compared to the difference signal before the directional enhancement processing,
Provide a feedback signal that is combined with the stereo input signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a stereo image enhancement system employing the directional servo circuit of the present invention; FIG. 2 shows details of the directional servo circuit of FIG. 1; The figure shows a modification in which part of the summation signal is boosted with the difference signal, and FIG. 5 shows our previous patent No. 4,747,669 (which corresponds to Japanese Patent Application No. 62-501080) which includes automatic echo control. )
FIG. 6 shows the characteristics of the reverberation filter of the circuit shown in FIG. 5, FIG. 7 is a block diagram of a multi-band servo equalizer used in a stereo improvement system, and FIG. FIG. 9 is a detailed block diagram of the multi-band servo equalizer of FIG. 7, and FIG. 10 is a block diagram of the multi-band servo equalizer used without a directional servo circuit. FIG. 11 shows a configuration in which the addition signal is dynamically boosted, FIG. 11 shows a method of combining the dynamically boosted addition signal and the processed difference signal and a directional servo circuit is used, and FIG. 12 shows the addition signal. 3 illustrates a form of a directional servo circuit employing a modified specification for augmentation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The system shown in FIG. 1 is essentially the same system as shown in the earlier patents mentioned above. However, FIG. 1 has been modified by including the directional servo circuit of the present invention.

The left and right channel stereo input signals L and R are supplied to a subsonic filter 1
Supplied through the 2 and 14, the stereo input signal L _in and R
and supplies the _in. The input stereo signal is supplied to a differential circuit 11 and a summing circuit 13 to provide a difference and sum signal (LR) and (L + R).

Incidentally, the stereo input signal L _in and R _in are (in all embodiments described in this document) directly from a stereo source, or usually supplied from indirectly difference signal and sum signal for broadcasting. In the latter case, the received sum and difference signals are processed as described above, and the signals L _in and R _in are obtained by adding and subtracting the sum and difference signals. The difference signal is supplied to a spectrum analyzer 17,
The analyzer provides a plurality of outputs indicating the relative amplitudes of the different difference signal components in a group within a preselected frequency band. The output signal of this spectrum analyzer is a dynamic differential signal equalizer.
This equalizer boosts the difference signal components in the frequency band where the difference signal amplitude is low. That is, the difference signal components in those frequency bands that are normally quiet are boosted by the equalizer 19. That is, the spectrum analyzer 17 applies a voltage corresponding to a preselected frequency band to the equalizer 19 as the output signal. For example, the equalizer 19 adjusts the attenuation of the selected frequency band based on the voltage from the spectrum analyzer 17 by a capacitor such as a voltage-controlled variable capacitance diode. More detailed construction operations are detailed in related Japanese Patent Application No. 62-501080.

The output of the spectrum analyzer is also supplied to a dynamic summing equalizer 21 which relatively boosts the summing signal component in a frequency band outside said band where the difference signal is quiet. The output of the dynamic difference signal analyzer 19 is also supplied to a fixed difference signal equalizer 18 for further equalization.

A servo loop for the difference signal processed by equalizers 18 and 19 is provided via gain control amplifier 22 and control circuit 30. This servo loop is described in detail in the aforementioned US patent application Ser. No. 62-501080 as several equalizers.
A control circuit 30, responsive to the unprocessed sum and difference signals (L + R) and (LR) and the output of the amplifier 22, i.e., the processed difference signal (LR) p, provides a control signal for controlling the gain of the amplifier. (CTRL). This configuration is such that the ratio of the processed difference signal to the unprocessed sum signal is predetermined and maintained at a substantially constant ratio.

Our earlier patent system includes reverberation control by circuitry within control circuit 30, which generates a reverberation control signal (RCTRL) which is provided to both dynamic signal equalizers 19 and 21. Input signal L _in and R _in, and processed sum signal (L + R) p is fed to the mixer 35.
In our patent application Ser. No. 62-501080, a processed difference signal (LR) p from a gain controlled amplifier is also provided to the mixer. In patent application Ser. No. 62-501080, the processed sum and difference signals are provided via potentiometers to adjust certain effects on the system. In earlier patents, the mixer operates on several signals input to the mixer and provides left and right output signals, defined by:

L _out = L _in + K ₁ (LR) p + K ₂ (L + R) p (1) R _out = R _in + K ₂ (L + R) p−K ₃ (LR) p (2) In the above equation, the value − K ₃ (LR) p is the same as + K ₃ (RL) p, and in an earlier patent by us, an inverter was supplied to the mixer and the processed difference signal (LR) p To provide a processed difference signal (RL) p. In our previous system, the processed difference signal (LR) p is part of the signal provided by the mixer and is the signal to the left speaker 36. The processed difference signal (RL) p is a signal supplied by the mixer, and is a signal to the right speaker 37. The signal from the mixer 35 is supplied to the speaker via the drive amplifiers 39 and 41. It should be noted that in FIG. 1, the speakers 36, 37 receive the output of the modified mixer having the directional enhanced output. In our earlier patent, the mixer output is defined by equations (1) and (2) but is not shown in the figure.

According to a feature of the invention, it is possible to remove the inverter from the mixer and place the inverter between the gain controlled amplifier and one of the directional servo circuits added to our previous patented system. . This configuration is shown in FIG. 1 and includes left and right additional directional servo circuits disposed between a gain controlled amplifier 22 and a mixer 35.
40 and 44 are shown. Except for the addition of an inverter and a directional servo circuit, the system of the present invention is the same as the system of the earlier patents by us described above.

As shown in FIG. 1, a gain-controlled amplifier
The processed difference signal (L-R) p from 22 is supplied as one input to a left direction servo circuit 40 and to an inverter 42 which supplies a processed right difference signal (RL) p. You. The processed right difference signal (RL) p is supplied to the right direction servo circuit 44 as one input. The right and left servo circuits 40 and 44 receive the left servo input signal L as a second input.
_in and the right servo input signal R _in are received. The servo circuit has at its output the directional enhanced left difference signal (LR) pe and the directional enhanced right difference signal (R-R).
L) Generates pe. The signals are provided via two ganged position switches 46, 48 which are alternatively connected to directional servo outputs or bypass lines 50, 52. By having the bypass line connected directly to the processed difference signal inputs (LR) p, and (RL) p, the directional servo circuit allows the combined switch to move to the second position, namely Switching to a position not shown disables or bypasses.

Since low frequency signals have a large energy component,
It is desirable to avoid the adverse effects that may be caused by sharp momentary bass on the right and left input signals R _in and L _in . Therefore, the right and left input signals are
Before being fed to 0,44, they are filtered through filters 57 and 59. These filters are relatively flat in the region above 150 Hz and have a sharp roll of 150 Hz.
f), and has a roll-off characteristic of 12 dB / octave in the region below f). Actually these are (about) 150Hz
And a high-pass filter with a fairly sharp cutoff.

Direction of the enhanced left and right difference signal (L-R) pe and (R-L) pe are stereo input signal R _in and L _in, and processed sum signal with (L + R) p, It is supplied to the mixer 35. The signal (L + R) p is a potentiometer (po
tentiometer) 56. The directional-enhanced left and right difference signals are passed to a mixer via an associated adjustable amplitude potentiometer 23a, 23b to simultaneously adjust the values of the left and right stereo difference signals to the mixer. Supplied. As a result, potentiometer 23
The adjustment of a and 23b adjusts the apparent width of the stereo sound image supplied by the mixer output. This mixer is composed of, for example, a well-known operational amplifier and an adder circuit including a resistor.
Each input signal is added with a predetermined gain and output. A typical configuration of this mixer is shown by the amplifiers 240 and 242 on the right side of FIG.

Due to the above-described input to the mixer 35, the mixer supplies the loudspeaker systems 36 and 37 with the outputs L _out and R _{out represented} by the following equations.
Supply.

L _out = L _in + K ₁ (L + R) p + K ₂ (LR) pe (3) R _out = R _in + K ₁ (L + R) p + K ₃ (RL) pe (3) where K ₁ and K ₂ , K ₃ is a constant.

In this system, the left difference signal (LR) p is
Although inverted before being supplied to the mixer via the right direction servo circuit 44, the (L-R) p of the earlier patented invention results in the signal (RL) p being generated in the mixer. To supply.

Details of the right and left directional servo circuits are shown in FIG. The two servo circuits are substantially identical except that one operates based on the left channel signal and the other operates based on the right channel signal, and thus will be described for only one channel.

Each directional servo circuit, processed difference signal for an increase of the input signals L _in and R _in (L-R) p or (R-L)
Provides an increase in volume within p.

Regard the left channel servo circuit shown in FIG. 2, the input signal L _in is supplied to an input peak detector 60 to provide a falling response (negatives going) output signal to an increase in L _in. Conversely, the detector 60 provides a rising (positives going) signal in response to a decrease of the signal L _in. The output of the peak detector is an inverted amplitude envelope of the input signal. The input signal whose peak has been detected is supplied to the addition point 64 at the inverting input of the operational amplifier 66 via the input resistor 62. Capacitor 68
Is connected between the amplifier output and its inverting input terminal, so that this amplifier can operate as an integrator. The inverting input of the amplifier, summing point 64, has a second input from the parallel RC circuit of feedback resistor 70. The peak detector 72 is the amplitude envelope of the input. The output of the amplifier 66 is a voltage controlled amplifier (voltage control
lled amplifier) 80, and the amplifier 80 outputs the signal (L-
R) p, that is, the gain-controlled amplifier 22 (first
The processed difference signal from FIG. The voltage controlled amplifier 80 produces as its output a difference signal output (LR) pe with enhanced directionality.

The differential feedback circuit 82 receives the processed difference signal (LR) p from the gain-controlled amplifier 22 as a first input, and an amplifier 80 as a second input.
Left difference signal output (LR) from the output of
Receive pe.

The differential feedback circuit 82 outputs the difference signal output (L−R) with the enhanced directivity pe minus the processed difference signal (L−R).
R) Provide a feedback signal on line 86 proportional to the value of p. This feedback signal is provided as an input to a feedback detector 72. The peak-detected (amplitude envelope) feedback signal is supplied to the inverting input of the amplifier 66 via the feedback resistor 70.

The feedback resistor 70 has a value that is two to three times the value of the input resistor 62. The ratio of the resistance values of resistor 70 and resistor 62 determines the directional enhancement provided by the directional servo circuit. This ratio is preferably between 2: 1 and 3: 1. If this ratio is less than 2: 1, there is almost no effect of the directional servo circuit, and if this ratio is more than 3: 1, the effect of directional enhancement is artificial and very superficial. become.
One or both of the resistors 62 and 70 can be variable resistors, which can limit the value for adjusting the amount of directional enhancement.

In the left direction servo circuit operation, it assumes that the input signal L _in is increased, therefore, the output of the peak detector 60 decreases. The reduced signal is supplied to the summing point 64, that is, the inverting input of the amplifier, which causes the output of the amplifier to increase. This is due to the amplifier operation holding all inputs (voltages) at point 64 substantially equal to the total inputs (voltages) at the grounded non-inverting input of the amplifier. As the amplifier output increases, the control voltage applied to the integration capacitor 68, which is the load of the amplifier, and the voltage-controlled amplifier 80 also increases. The gain of the amplifier 80 is 1 (unity) when there is no control input from the amplifier 66. This gain will never be less than one and will increase as the control signal from amplifier 66 increases. With the increase in the gain of the amplifier 80, there is a concomitant increase in the directional enhanced left difference signal output (LR) pe. The increased output of the voltage controlled amplifier is applied to the processed difference signal (L−
R) the feedback peak detector 72
Supply a feedback signal to the Accordingly, the peak detector 72 supplies a signal having an increased polarity opposite to the polarity of the signal from the peak detector 60 to the inverting input of the amplifier 66.

The two voltages from each peak detector are combined in a resistance summing network formed by resistors 62, 70 to provide a combined signal. This signal stabilizes to a value equal to the grounded input of the non-inverting input of the amplifier due to the feedback of the amplifier through capacitor 68.
Assuming that the ratio of the resistance values of the resistors 70 and 62 is 3: 1, the voltage of the feedback signal whose peak is detected from the feedback peak detector 72 is about three times the signal voltage from the input peak detector 60. At this time, the amplifier input signal at the addition point 64 is stabilized. This arrangement provides a controlled amount of feedback and produces a controlled increase in the output of the integrating amplifier. This increase in output of amplifier 66 causes an increase in the control voltage supplied to voltage controlled amplifier 80.

Preferably, the voltage controlled amplifier 80 responds only to changes in the reference signal that is the output of the peak detector 60. The output of a voltage controlled amplifier with a genin that should never be less than one will never be less than the input (LR) p. Therefore, the feedback signal from the differential circuit 82 causes the directional servo circuit to respond only to a change in the reference signal. Reference signal (output of peak detector 60)
If there is no change, there is no control signal to the amplifier 80 and its output is the same as its input, so there is no feedback signal provided to the peak detector 72. By using the differential circuit 82, (L-R) changes in p amount (e.g., a difference between the output and the input of the amplifier being voltage-controlled), with respect to the input reference signal L _in, can be accurately controlled.

As a result, an increase _in the input signal Lin produces an enhanced (exaggerated) increase in the processed difference signal, and voltage-controls the directional enhanced difference signal (LR) pe. Occurs at the amplifier output. With resistor 70 selected to be two to three times the resistance of resistor 62, the increase in processed difference signal amplitude is two to three times the increase in input signal amplitude. L _in
Does not produce any enhanced (LR) pe reduction. Because the gain of amplifier 80 is
It is because it does not become 1 or less. As described above, the left difference signal having the directionality enhanced is supplied to the mixer via the bypass switch 46 and the stereo audio image width adjustment potentiometer 23a.

Capacitor connected via feedback resistor 70
71 provides an increased rate of feedback on the fast-moving phenomenon. For relatively slow changes in the output of peak detector 60, capacitor 71 does not operate effectively. However, with respect to the rapid change of the output, the feedback from the peak detector 72 is transmitted at a high speed through the capacitor 71, thereby enhancing the response time of the feedback.

The operation of the right-direction servo circuit is the same as the above-described operation, but, of course, this servo circuit includes R _in and (RL)
operates in response to p (received from inverter 42),
It provides a directionally enhanced right difference signal (RL) pe which is supplied to the mixer via the bypass switch 48 and the stereo audio image width adjustment potentiometer 23b.

The right servo circuit includes the same components as the left servo circuit, and is identified by the same reference numeral with the prefix 1, the left channel enhanced peak detector 60 corresponds to the right channel peak detector 160, Left channel
Amplifier 66 corresponds to right channel amplifier 166, and so on. Therefore, the right channel directional servo circuit includes the peak detectors 160 and 172, the summing resistors 162 and 170, the capacitor 171, the summing point 164, the integrating amplifier 166, and the feedback capacitor.
168, a voltage controlled amplifier 180, a differential circuit 182, and a feedback line 186, all of which are identical to the correspondingly numbered components of the left channel described above. As is well known in the art, this differential amplifier 6
6, 166 are integrators (average circuits) in the feedback loop
Is composed. This corresponds to a first order lag element in automatic control and is well known to those of ordinary skill in the art.

Capacitors 71 and 171 of FIG. 2 cooperate with feedback capacitors 68 and 168 via differential amplifiers 66 and 166,
Two peak detectors 60, 72 and 160, 172 for each channel
Hold the desired ratio of the signals supplied from the. Capacitor
The capacity of 71 is about four times that of the capacitor 68. For example, the capacitor 71 is 16 microfarads, and the capacitor 68 is 4.7
Microfarad. The ratio of the impedance of the capacitors 168 and 171 is the same. Therefore, desired directionality enhancement can be obtained even for high-speed movement of sound.

In some situations, especially in television and cinema, when shooting or approaching vehicles or text-moving devices, or such objects appear with accompanying commentary in the center of the audio image, the Increasing the directionality of the sound may overwhelm or negate the central commentary. To avoid this situation, the central commentary can be dynamically enhanced or boosted, especially to counteract this tendency. In order to achieve such sound enhancement at the center, the configuration shown in FIGS. 3 and 4 is employed. These figures show the processed summed signal (LR) applied to the inputs of the voltage controlled amplifiers 80, 180 of each channel.
4 shows an exemplary circuit for adding a portion of p. This circuit achieves directional enhancement not only for the processed difference signal, but also for a portion of the processed sum signal. (L +
R) The addition of a portion of p is shown in FIG. Directional enhanced (L + R) pe component separation and independent amplitude control is shown in FIG. A dynamic enhancement of a portion of the sum signal, and other arrangements for combining the signal with the directional enhanced difference signal, are shown in FIG. 12 and the description below.

The circuits of FIGS. 3 and 4 show another arrangement for providing an input to a directional servo circuit. This can be used in place of the input shown in FIG. 2 when the system is configured so that the central voice is not canceled. FIG. 4 shows the process of correcting the directional servo output and other signals used in FIG.

As shown in FIG. 3, the processed sum signal (L + R) p from the dynamic sum equalizer 21 (FIG. 1)
Is supplied to an attenuation potentiometer 202 from which a signal K (L + R) p is obtained. Here, a feedback of about 3: 1 directional servo circuit is employed. As mentioned above, K
Is of the order of 1/4, whereby potentiometer 202 provides a processed sum signal having an amplitude of about 1/4 of the amplitude of the processed sum signal provided from dynamic sum equalizer 21. . The attenuated addition signal is fed through resistors 204 and 206 to first and second inversion operation amplifiers having feedback resistors 212 and 214, respectively.
It is supplied to each inverting input of 208 and 210. The second signal supplied to the inverting input of the amplifier 208 via the resistor 216 and the inverter 215
The signal is the processed difference signal-(LR) p from the gain controlled amplifier 22 of FIG. Amplifier 20
For the amplifier 8 and the amplifier 210, a well-known inverting type adder using an operational amplifier is engraved. For example, the amplifier 208 includes a resistor 2
Since 04, 212, and 216 are equal, each input signal is added with a gain of 1, inverted in polarity, and output. Therefore, the output signal of the amplifier 208 is (L−R) p−K (L + R) p.

The second signal provided to the inverting input of amplifier 210 via resistor 220 is the output of amplifier 208. But the amplifier 210
Output phase is opposite to the output of the amplifier 208 (second
As shown in the amplifier 210, (L + R) p is the same as the inverter 42 shown is used to invert (LR) p in the lower channel of FIG.
It is necessary to adjust the component values. This is for resistors 220 and 214
Is the same as that of the resistor 206, which supplies the processed sum signal to the amplifier 210. This adjustment of the resistance produces a processed sum signal at the output of amplifier 210 (obtained from the processed sum signal component of potentiometer 202),
This is doubled. However, the other input through the resistor 220 of the amplifier 210 (from the output of the amplifier 208) is also the processed anti-phase sum signal component -K (L + R) p (related to the phase of the processed sum signal of the potentiometer 202). ), The two processed antiphase sum signals are effectively subtracted in amplifier 210, the net result being the correct phase component -K (L + R) p at the output of amplifier 210. The processed addition signal component is supplied from the potentiometer 202 via a resistor 206 having a relatively small resistance value.
Via the output of the amplifier 208. Therefore,
The resulting output of amplifier 210 is (RL) p-K (L +
R) p and the output of the amplifier 208 are (LR) p−K
(L + R) p. Therefore, the left and right channel signals are
The same amount of the processed sum signal is added. As described above, this is a part of the processed sum signal, but is used to eliminate the effect of the central sound being drowned out.

The output of amplifier 208 is provided to voltage controlled amplifier 80 which produces an output on line 230, such as signal (LR) p in FIG. Similarly, the output of amplifier 210 is provided to the input of a voltage controlled amplifier 180 that produces an output on line 232, such as the output of inverter 42 in FIG. The other components of the directional servo circuit shown in FIG. 2 (not shown in FIG. 3) are all used in the configuration of FIG. FIG. 3 shows only an example of changing the input to the voltage-controlled amplifier of FIG. 2, and the other parts of the directional servo circuit are the same as those shown in FIG. However, the servo output is processed differently, as will be explained later with reference to FIG.

With the enhancement of the central stage, the directional servo circuit
Operates on the difference signal and a portion of the sum signal, and
Directional enhancement is effectively applied to the sum and difference signals, but more strongly for the difference signals.

The amplitude of the boosted and enhanced added signal component (L + R) pe which occurs together with the boosted and enhanced difference signal components (LR) pe and (RL) pe is determined by the output line of the circuit of FIG. It is desirable to control 230,232. That is, it is desirable to be able to control the relative amplitude of these two components. This is because the enhancement or boost of the added signal by the directional servo circuit may be too large. Therefore, the boosted and boosted sum signal is
As in the circuit shown, it is separated, attenuated, and combined with other components in the mixer. In order to independently control the amplitude of the enhanced summation component (L + R) pe, this component is the enhanced difference signal component (LR) at the outputs 230, 232 of the directional servo circuit of FIG. pe and (R-
L) must be separated from pe.

As shown in FIG. 4, the left channel directional servo circuit output on line 230 of FIG. 3, and the line of FIG.
The right channel directional servo output on 232 is a paired stereo audio image width adjustment potentiometer 223
a, 223b, and these potentiometers
Corresponds to (used instead of) potentiometers 23a, 23b in the figure. In the configuration of FIG. 1, to control superficial stereo sound image width, the output of these combined potentiometer, R _in, together with L _in and (L + R) p, it is fed directly to the mixer. 3 and 4 are different. Here, a part of the added signal is processed and enhanced, and the outputs of the stereo audio image width adjusting potentiometers 223a and 223b are supplied to the mixer as shown in FIG. This mixer comprises amplifiers 240 and 242. The circuit shown in FIG. 4 separates the processed and enhanced sum signal component to control its amplitude, independent of the amplitude of the processed and enhanced difference signal component. As will be explained later, the mixer also receives the stereo inputs L _in and R _in, but does not receive the processed sum signal (L + R) p. Instead, the mixer receives the processed and enhanced sum signal (L + R) pe via the circuit of FIG.

The signals from potentiometers 223a and 223b are (LR) pe-K (L + R) pe and (RL) pe-K, respectively.
(L + R) pe (the constant K of these components indicates the attenuation caused by the width adjustment potentiometer). These signals are coupled to a voltage divider constituted by 244 and 246, so that signal components having different antiphases are eliminated from each other at a coupling portion 248 of these resistors. That is, since the values of the resistors 244 and 246 are equal, (LR) pe and (RL) pe are added to the differential amplifier 250 with the same amplitude and opposite polarities, so that they are canceled each other. . The remaining addition signal at the node 248 is supplied to an inverting input of a differential amplifier 250, and the differential amplifier outputs the added value of the signal supplied to this amplifier via voltage dividing resistors 244 and 246. Occurs on output. By removing the difference signal component of the opposite phase by this addition, the amplifier
The output of 250 is effectively + 2K (L + R) pe. Thus, the processed and enhanced sum signal component is provided independently of the processed and enhanced difference signal component.

The addition signal is the second independent amplitude control potentiometer 266
(The first potentiometer is the potentiometer in FIG. 3.
By feeding through (202), the amplitude is adjusted appropriately. The output of the potentiometer generates an amplitude adjustment process and an enhanced addition signal component + K ₁ (L + R) pe. Here, the constant K ₁ is the amplitude of the sum signal component, are used to simply indicate that differs from the amplitude of the sum component generated from the directional servo circuit.

The left channel mixer is an amplifier 24 having a resistor summing network input comprising resistors 280, 282, 284, 286.
All these resistors are commonly connected to the non-inverting input of the amplifier and to the amplifier feedback resistor 288. After inversion by the inverter 241, the output of mixer amplifier _{240, Lout = L in + K 4} (L + R) pe + K 5 (L
-R) pe. This signal can be provided to the left channel speaker if desired. Resistance 280 receives an input signal L _in the left-channel stereo. Resistance 282
Receives the output of the amplifier 250, which is the processed and enhanced sum signal component before being attenuated by the potentiometer 266. Resistor 284 is supplied with the processed and combined difference and sum signal components from the wiper arm of potentiometer 223a, and resistor 286 receives the processed and enhanced sum signal component, but the component Is selectively attenuated by potentiometer 266. Resistance 280,
282, 284 and 286 and feedback resistor 288 are in a proportional relationship, providing the desired amplitude relationship of some inputs to mixer amplifier 240. In the preferred embodiment, the resistors have the following values: Resistance 280 10K,
Resistance 282 10K, Resistance 284 5K, Resistance 286 5K, Resistance 286 5K,
Resistance 288 26K. The addition component whose amplitude is independently adjusted from the potentiometer 266 is supplied to the mixer 240 via the resistor 286. Therefore, the size of the combined portion of the addition signal supplied to the amplifier via the two resistors 282 and 286 can be effectively and independently controlled.

The right channel mixer amplifier 244 is
It is substantially the same as a mixer amplifier and its summing network. Therefore, the right channel mixer amplifier 242
Resistance 290, 292, 294, 296 and feedback resistance 298
, All of which are provided to the inverting input of an amplifier, such as amplifier 240, whose non-inverting input is grounded. After the output of the right channel mixer amplifier 242 is inverted by the inverter 243, R _out = R _in + K ₄ (L + R) pe + K ₅ (R−
L) pe. This signal is amplified and provided to the right speaker if desired. The resistor 290 is the right stereo input signal R
to enter _in. The resistor 292 inputs the added signal component that has been amplified and enhanced from the output of the amplifier 250. Resistance 249
Inputs the processed and enhanced difference signal component on line 264 of the right channel, and resistor 296 is connected to potentiometer 2 which is also provided to resistor 286 of the left channel, as described above.
Receive the output of 66. Resistance 290, 292, 294, 296, 298
Is the same as the relevant value of the corresponding resistance of the left channel, so that in the embodiment the resistance value is as follows: 290 10K, 292 10K, 294 5
K, resistance 296 5K, resistance 298 26K.

The relationship values of these resistors affect the increase of the difference signal amplitude with respect to the sum signal amplitude at the input of the mixer. This relative boosting of the difference signal is not part of the difference signal enhancement achieved by the equalizers 18, 19, 21 or the servo equalizer of FIG. Has no effect) and is merely provided as a compensation for a fixed amplitude reduction of the difference signal. Such amplitude reduction is provided by an amplitude control circuit (not shown) before enhancing the difference signal. This fixed amplitude reduction (not shown) maintains the enhanced difference signal amplitude below a value at which amplitude clipping, which may occur in various amplifiers, occurs.

The directional servo circuit described above is particularly useful in the stereo sound field enhancement circuits of the earlier patents mentioned above. And
The principles of the present invention can also be applied to other stereo systems that provide left and right channel audio for which directionality should be properly enhanced.

Stereo Enhancement by Multi-Channel Servo Equalization The configuration of the directional servo circuit shown in FIGS. 3 and 4 generates a dynamically enhanced sum signal on the wiper arm of potentiometer 266. This signal can be effectively used directly in the improved configuration of the stereo enhancement system of FIG. 1, and also in the configuration of the simplified enhancement system of FIG. 1 shown in FIG. Can be used The stereo enhancement system as shown in FIG. 1 (except for the directional servo circuit of FIG. 1) is further described in our earlier patent 4,748,669 relating to the Stereo Enhancement System, assigned to the assignee of the present invention. It is described in detail.
The disclosure of this patent is incorporated into this document and is fully explained. In our earlier patented stereo enhancement system, the enhancement of the stereo sound field is achieved by an equalizer circuit that effectively boosts the signal components in the lower and upper frequency bands of the difference signal, and the processed difference signal. And a servo circuit that maintains a selected ratio of the sum signals. These circuits operate on artificial reverberations that can be introduced at the input. Thus, in my earlier patents, for artificially introduced reverberations, various forms of automatic reverberation control are employed to eliminate or compensate for the undesirable effects of stereo sound field enhancement (eg, undesirable boost).

In the system of FIG. 5, which is also our earlier application and is also shown in FIG. 4, the left and right channel stereo inputs are subsonic filters 312, 314.
, And then to difference and adder circuits 311 and 313 to provide difference and adder signals (LR) and (L + R), respectively. These signals are supplied to a fixed difference signal equalizer 315 and a fixed addition signal equalizer 317. The output of the fixed addition signal equalizer is supplied to an amplifier 325 whose gain is controlled under the control of the signal CTRL from the control circuit 340.
The gain controlled amplifier 340 receives the signals (L + R) and (LR) as inputs and receives the feedback signal occurring on line 341 from the output of the voltage (gain) controlled amplifier 325. . The control circuit 340 also provides a reverberation control signal RCTRL, which provides a small boost to the signal (L + R) via a gain controlled amplifier 327 to generate a processed sum signal (L + R). Supplied for. An amplifier that is the processed difference signal
The output of 325 is provided to provide a processed difference signal (LR) p via an echo control filter 329 controlled by an echo control system RCTRL. This processed difference and sum signal is provided to the combined width control potentiometer 319, which provides the processed difference and sum signal to the mixer 321.
The mixer also receives the left and right channel stereo input signals, combines the signals, and provides left and right output signals Lout, Rout on lines 322, 323, respectively.

The reverberation filter 329 effectively attenuates certain intermediate frequency bands in the presence of perceived artificial reverberation. In general,
A single vocal or performer is recorded to appear at the center of the stage, so that the performer's voice initially appears in the sum signal (L + R). The processed difference signal at the output of amplifier 325 is added to the summed signal to maintain a predetermined fixed ratio between the processed difference signal and the summed signal (all described in detail in our earlier patent). Servo control is effectively performed. Thus, an increase in (L + R), such as that caused by an artificially induced reverberation, causes an undesirable increase in the enhanced effect of the system on certain difference signal components. Thus, when too much reverberation is sensed, reverberation filter 329 is used to selectively attenuate the difference signal in the band of about 300 to 4,000 Hz.

In order to sense too much reverberation, our previous patent system senses an increase in the sum signal (L + R) from a preselected and proportionate state, such that (L
The system operates based on the assumption that the increase in + R) is due, at least in part, to artificially generated reverberations. In addition to attenuating the intermediate frequency band in response to the sensed reverberation, this sum signal is boosted (to a lesser extent) by amplifier 327 under control of RCTRL.

The reverberation filter 329 has the features shown in our earlier patent and described in FIG. That is, each has a crossover point of about 300 Hz and 4000 Hz, and has a sharp cutoff (cu
a low-pass channel filter, indicated by curve 326, a high-pass channel filter curve, indicated by curve 328, and a mid-band channel filter, indicated by 330, having a rise time of t off). The center channel of this echo filter provides variable attenuation under the control of the signal RCTRL from the control circuit 340, so that the response of the center channel is shown in FIG. 6 as the amount of echo reflected changes. Thus, the curve 330 changes to 330a or 330b.

In order to improve the circuit of FIG. 5 more automatically, more simply, and at a lower cost, the applicant has developed a stereo enhancement system which provides the desired effect of FIG. Was done. The improved configuration is shown in FIG. This configuration uses a low-frequency servo controlled equalizer instead of the fixed addition and difference signal equalizers 315 and 317, gain controlled amplifiers 325 and 327, control circuit 340, and reverberation filter 329 of FIG.

As shown in FIG. 7, the left and right input signals are
1 and an addition circuit 413, and the difference and addition signal (L−
R) and (L + R) are provided, respectively. These signals are
For the sum and difference signals, instead of feeding to a dynamic or fixed equalizer, the sum and difference signals are equalized 415, 4 with high and low pass servo control.
Supplied to 17. Therefore, the difference signal is supplied to both the low-pass and high-pass servo-controlled equalizers, and the sum signal is also supplied to both the low-pass and high-pass servo-controlled equalizers. (In this connection, the sum signal is used only as a reference signal, as shown below.) The output (LR) pl of these two separate servo-controlled equalizer channels that have been processed in the low and high ranges And (LR)
ph is combined in a summing circuit 420 to provide a processed difference signal (LR) p. This signal and the addition signal (L
+ R) is supplied to the left and right directional servo circuits 440 and 444. These directional servo circuits are basically the same as the directional servo circuit of FIG.
This is exactly the same as the configuration of the directional servo circuit shown in FIGS. The inputs to these servo circuits are, as shown in FIG. 3, an addition signal (L + R) from the addition circuit 413 supplied to the potentiometer 202 in FIG. 3 and an addition amplifier 420 supplied to the inverter 215 in FIG. Difference signal (L−
R) Indicated by p. Similarly, the signals Lin and Rin are supplied to the directional servo circuit via the filters 457 and 459, respectively, as described above. Most of the components of the system of FIG. 7 are identical or correspond to the components of FIG. 1, and these components of FIG. 7 are used in FIG. 1 except that a reference number is added with a suffix of 4. Identified by the same reference number as the reference number given. Therefore, for example, the addition circuit 413 of FIG.
Corresponds to the adding circuit 13 in FIG. 1, and the differential circuit in FIG.
1 corresponds to the differential circuit 11 in FIG. Similarly, corresponding elements of the circuit of FIG. 5 use the same reference numbers as in FIG. 1, but in FIG. 5 these numbers are pre-fixed by the number 3 so that, for example, The adder circuit 313 in FIG. 5 corresponds to the circuits 13 and 413 in FIG. 1 and FIG. 7, respectively.

It is understood that FIG. 7 comprises a modified version of the circuit of FIG. That is, in this circuit, instead of the equalizer, the gain-controlled amplifier, the control circuit, and the reverberation filter, an equalizer that is controlled by a low-frequency servo with an addition circuit 420 and an equalizer that is controlled by a high-frequency servo are used,
Further, in the method shown in FIG. 1, the left and right directional servo circuits are arranged between the equalizer processing circuit and the mixer. The outputs of the left and right directional servos 440, 444 are provided to a combined width adjustment potentiometer 423a, 423b (corresponding to the corresponding element 223a, 223b in FIG. 4). Outputs of the width adjustment potentiometers 423a and 423b are supplied to a separation and amplitude adjustment circuit 445 and a mixer 447 which will be described in detail with reference to FIG. The left and right stereo outputs supplied to the speakers are supplied as outputs of the mixer 447, with or without amplitude amplification.

In the configuration of FIG. 7, all difference signals are equalized (eq
Instead, the signal is applied to the reverberation filter of FIG. 5 with the characteristics shown in FIG.
It is further divided into several different frequency bands, with some bands separated. Accordingly, a low frequency servo controlled equalizer 417 that handles low frequency signals up to about 237 Hz is provided. High-frequency servo controlled equalizer 415 in FIG.
Is provided to handle high frequency components above about 7,000 Hz. The center channel comprising line 416 directly applies the difference signal (LR) directly to summing amplifier 420, as shown below.
(Via resistor 421). Preferably, the low and high frequency bands do not overlap and are separated from each other by a center band extending between about 273 Hz and 7,000 Hz. By equalizing the low-pass and high-pass bands independently and simultaneously, the high- and low-pass bands of these difference signals are compared with the low- and high-pass bands of the corresponding summation signal. By servoing, any undesirable enhancement of the intermediate frequency band caused by artificially generated echoes can be avoided. As a result, by applying enhanced servo control only to the low and high passbands, stereo sound field enhancement provides unnecessarily and inappropriately unenhanced sound caused by artificially generated reverberation. can do. As explained in our earlier patents, these low and high frequency bands are those frequencies where the difference signal component is generally small in amplitude, for example, the frequency band where the difference signal speech is quiet.

FIG. 8 is a diagram showing an effective response of the high-frequency and low-frequency servo equalizers of FIG. Curve 426 (corresponding to curve 326 in FIG. 6) has a cutoff frequency of about 237 Hz and is 6 dB / octav
Shows a low pass servo equalizer attenuated by e. Curve 428
The response curve of the high-pass servo equalizer channel (corresponding to curve 328 in FIG. 6) rises with a relatively gentle slope of 6 dB / octave and has a substantially flat characteristic in the band above about 7,000 Hz. Is shown. Curve 430 shows the response characteristic on the relatively attenuated, flat, resistive line 416 of FIG. Thus, it will be appreciated that the low and high pass servo equalizers of FIG. 7 provide the desired filtering corresponding to the reverberation filter 329 without the deleterious effects of mid-pass servo control of the difference signal component. There will be. As explained below, this circuit effectively provides varying amounts of boost in its high and low frequencies, maintaining the aforementioned ratio of processed difference signal and sum signal independently in each band. .

Details of the low and high frequency servo equalizers are shown in FIG. The left and right input signals are supplied to the difference and addition circuits 411 and 413, respectively, as described above. The difference signal (LR) from circuit 411 is provided to a low-pass filter 450 having the characteristics of curve 426 in FIG. The output of amplifier 452 is provided to a non-inverting peak detector 454, the output of which provides a DC signal indicative of the amplitude envelope of the low pass servoed difference signal component. This signal is unipolar,
The signal is supplied to the addition amplifier 458 of the control signal generation circuit 460 via the addition resistor 456. Circuit 460, with some simple changes, performs the integration function and roughly corresponds to control circuit 50 of FIG. 3 of our earlier patent 4,748,669. This circuit also has several feedback paths for the amplifier 458,
Provides the limiting voltage of the integrating and Zener diode.

The addition signal (L + R) from the addition circuit 413 is
The same is applied to a low-pass filter 462 having the same characteristics as 50, and then to an inverted peak detector 464. The detector 464 is connected to the amplifier 458 via the second addition resistor 466.
Supplies a second DC input, the signal of which is of opposite polarity to the signal supplied to resistor 456. The output of the amplifier 458 is fed back to the voltage control amplifier 452 as a control signal,
Thereby, the output of the amplifier 452 on line 470 is servo controlled and processed of the difference signal low pass component (L-
R) supply pl. This signal is supplied as a first input to summing amplifier 471 (corresponding to summing amplifier 420 in FIG. 7).

The signal (LR) includes a high-pass filter 472 and is provided via a high-pass equalizer channel having a response characteristic indicated by curve 428 in FIG. The output of filter 472 is provided as an output on line 476 to a second voltage controlled amplifier (VCA) 474 that provides a high pass servo controlled equalized difference signal component (LR) ph, and The difference signal component is supplied to a summing amplifier 471 as a second input.

The output of the voltage controlled amplifier 474 is also the non-inverted peak detector 4
The output of the detector supplies a DC signal indicating the amplitude envelope of the difference signal component from the amplifier 474 which has been subjected to the high-pass servo control and processed.
The output of 8 is supplied to the second control amplifier 48 via the first addition resistor 480.
Supplied to 2 inputs. The control circuit of the amplifier 482, which is shown surrounded by a dotted frame 484, is a low-frequency servo equalizer
This is the same as the channel control circuit 460. The second to amp 482
The 2DC input is provided via the second summing resistor 486 from the output of the inverted peak detector 488, which is shown in FIG.
High-pass filter with response characteristic indicated by 28
490 output is received and its response characteristic is high-pass filter 4.
It has the same response characteristics as 72. These peak detectors
The amplitude envelope of each of these input signals is output. The input to the high-pass filter 490 is the addition signal (L + R) from the addition circuit 413. The output of amplifier 482 is fed back in the same manner as the output of low-pass channel amplifier 458 to control the operation of voltage-controlled amplifier 474, and thus the high-pass signal component (L) on processed and servo-controlled line 476. -R) Control the magnitude of ph. Line 47
The servo-controlled and processed low-pass and high-pass difference signal components on 0, 1476 are combined with the unprocessed difference signal (LR) supplied to summing amplifier 471 via resistor 494. Therefore, the processed difference signal (L-
R) p occurs, and this difference signal contains low-pass and high-pass difference signal components that are separated, mutually and independently servo-controlled and equalized. The processed difference signal is also simply attenuated by resistor 494, wide band (the whole voice band of this system)
Contains the difference signal component.

9, the outputs of the resistance summing networks 456, 466 are provided to the inverting input of an amplifier 458 via a switch 457 which operates in response to the output of a comparison circuit 459. This comparison circuit compares the output of the inverted peak detector 463 receiving the addition signal (L + R) with the output of the non-inverted peak detector 461 receiving the difference signal (LR). The output of the comparison circuit 459 is also the switch 46 connected between the inverting input of the amplifier 482 of the circuit 484 and the resistors 480, 486 of this circuit.
3, a similar switch (not shown) connected between the inverting inputs of the directional servo integration amplifiers 66, 166 (FIG. 2) and the input resistors of these amplifiers, if desired. Used to operate The purpose of these switches is to disable the operation of this enhancement circuit (and directional servo circuit if desired) in the absence of a stereo signal. Switches 457, 481 operate in a manner similar to the corresponding switched zener diode in the feedback circuit corresponding to the integrating amplifier of our earlier patent. In the circuit shown in FIG. 9, the output of the difference signal peak detector 461, which is substantially a stereo detector, is connected to the resistance addition circuit 4
The output of the sum signal peak detector 463 at 65 and 467 is compared. When the output of the peak detector 461 is a predetermined value, that is, a value such as 1/5 of the output of the peak detector 463 (for example, the difference signal is a value much smaller than the sum signal), the comparator
The output of 459 opens switches 457, 481, thereby disabling the stereo enhancement (directional servo circuit, if desired). When the value of the stereo signal increases, such as when the difference signal envelope amplitude at the output of the peak detector 461 is actually greater than 1/5 of the sum signal envelope amplitude at the output of the peak detector 463, the comparator output is Switches 457, 481 are closed, and the augmentation circuit operates as described above. Ratio of addition signal and difference signal 5: 1
Is defined by the relative ratio of the resistors 465, 467. This ratio can be easily changed if desired.

In each low-pass and high-pass servo equalizer, each low-pass and high-pass component of the difference signal is
8, 482 is effectively independently compared with the corresponding low-pass or high-pass component of the summation signal at each resistance summing network input. In each case, the resistance of the summing network is selected to maintain the desired fixed relationship (amplitude ratio) for the processed difference signal component of a particular band to the summed signal of the corresponding band. In general, it is desirable that the resistance of the resistor 456 supplying the processed difference signal component is at least the same as the resistance of the resistor 466 supplying the added signal component. The ratio of resistors 456 and 466 is about
Desirably, it is on the order of 1: 1 to about 3: 1 (in the latter case, the resistance 456 is larger). Resistance 456 to resistance 466
When the ratio is set to a large value (this ratio can be selectively varied within the limit range, but fixed for a given system), the servo operation will produce an unprocessed low-pass sum signal component , The amplitude of the low-pass processed difference signal component is maintained larger and larger. The system shown in FIG. 9 is used in the directional servo circuit shown in FIGS. 3 and 4, or FIG. 12, wherein the ratio of resistors 456 and 466 is 1:
One can be used. This is because the directional servo circuit itself provides additional enhancement and boost of the difference signal component.

The above consideration, which determines the relative ratio of the input resistances 456, 466 of the low-pass channel, is based on the input resistance 48 of the high-pass channel.
The same applies to 0 and 486. Therefore, these resistors are employed in ratios ranging from 1: 1 to 3: 1. That is, the resistance
By making 480 at least the same or greater than the resistance 486, the high-pass servo control and the equalized (processed) difference signal component will be larger than the high-pass band raw sum signal component. .

The output of summing amplifier 471, which is the processed signal (LR) p, is provided to the directional servo circuit as described in connection with FIG. 3 (or shown in FIG. 3 and described below). Supplied to the described directional servo circuit). Therefore, the output of the addition amplifier 471 is, as described above, the gain control amplifier 2
Instead of being received from 2, it is supplied to the inverter 215 of FIG. Similarly, the addition signal from the addition circuit 413 (at this time, the processed signal has not been received) is supplied to the potentiometer 202 of FIG. 3 instead of the signal (L + R) p shown in FIG. . With respect to these signals from the circuit of FIG. 9 to the circuit of FIG. 3, as described above, the directional servo circuit outputs signals on lines 230 and 232,
4 are identical to the circuit elements of FIG. 3 which are provided to the circuit of FIG. 4 and provide the desired system output.

The system described in this regard provides significant servo-controlled boosting of the low and high frequency bands of the difference signal, each two bands being boosted independently of each other. Such boosting or boosting occurs to the extent that it overwhelms or drowns out the center stage sound, as performed by the sum signal (L + R). That is, the systems described so far cause the center stage sound to be substantially fading into the background to the listener, as manifested in the sum signal (LR). Therefore, for this simplified servo equalizer system, it is desirable to provide a dynamic boost of the sum signal (L + R). As described above, such a dynamically boosted sum signal is provided to a directional servo circuit, and in particular, to the wiper arm of potentiometer 266 in FIG. This circuit provides a dynamic boost of the sum signal. Because, the nature of the directional servo, as described above, senses an increase in the input stereo signal and provides a greater increase in the resulting processed sum and difference signals. Thus, when the servo equalizer configuration of FIG. 9 is applied to provide the input of a directional servo circuit, the wiper arm of potentiometer 266 is slightly adjusted (the wiper arm has a dynamically boosted wiper arm). Only the added signal component occurs), providing a slight increase in the amplitude of the signal appearing on its wiper arm. Accordingly, this directional servo circuit, which effectively generates a signal including a dynamically boosted sum signal component in the potentiometer 266, is used together to improve and simplify the servo equalization shown in FIG. To compensate for the separated band.

FIG. 9 shows servo equalization in two frequency bands, a low-pass band and a high-pass band, but it is clear that other bands can be used. Each band, low pass band and high pass band described can be divided into two or more separate high or low pass bands, each band being identical as shown in FIG. Servo elements. Thus, for example, if the low-pass band is divided into two different low-pass bands, servo equalization will provide two filters 450, two amplifiers 452, and two for each element in the low frequency channel. It provides the other two elements shown in FIG. 9 for the low pass band, and all these channels are added as will be apparent to those skilled in the art.

The improved enhancement due to the separation band of the servo equalization has been described in connection with a system using fixed addition and difference equalization, as shown in FIG. The system shown in FIG. 1 uses both dynamic sum and difference signal equalizers 21 and 19 and fixed difference signal equalizer 18. Where the servo equalization configuration is used in a system such as that shown in FIG. 1, a dynamic sum and difference equalizer is still used, while the system of FIG. Controlled amplifier 22 and control circuit
Instead of the circuit including 30, it is used with an input to a directional servo circuit as described in connection with FIGS. 9 and 3.

The separate low and high pass servo equalization bands of FIG. 9 can be applied to a system using the directional servo circuit of FIGS. This is because the circuit of FIG. 4 provides the necessary components used in the processing arrangement of FIG. The necessary component is the above-described dynamically enhanced addition signal component in the potentiometer 266 of FIG.

However, the separate band servo equalizer configuration of FIG. 9 need not be used in a directional servo circuit, but can be used in systems without any directional servo circuit. In such a case, a circuit must be provided that generates a dynamically enhanced or dynamically boosted sum signal component with respect to the coupling of the dynamically boosted servo equalizer to the high and low pass bands. . A circuit that provides such a dynamic boost of the sum signal component and does not employ a directional servo circuit is shown in FIG. 10, which receives the left and right stereo input signals and provides the sum signal output (L + R). . The sum signal is provided to an inverted peak detector 520 that provides an amplitude envelope of the sum signal, and is provided via a first summing resistor 524 to the inverting input of summing amplifier 522. Amplifier 5
22 has a capacitor 526 in the feedback loop between its output and the inverting input to achieve input integration.
The output of amplifier 522 is on line 528 and the voltage controlled amplifier 530
And a dynamic control signal for controlling the gain of. This amplifier 530 receives the addition signal (L + R) from the addition circuit 513 as an input. Other VCs described here
Like A's, amplifier 530 has a minimum gain of one. The feedback signal from the gain adjusted sum signal that occurs at the output of amplifier 530 is provided via line 532 to the input of non-inverting peak detector 534. At the output of this detector 534, a DC signal is generated that indicates the amplitude envelope of the dynamically adjusted sum signal. This envelope, as in the case of other summing amplifiers such as the amplifiers 458 and 482 in FIG. This is supplied to the second resistor 536. The resistance ratio of the resistors 536 and 524 is preferably about 2: 1 (the resistance of the resistor 536 is about twice the resistance of the resistor 524).

With respect to the configuration shown in FIG. 10, the increase in signal (L + R) is sensed and effectively amplified by the circuit shown, causing a greater increase in the output of the voltage controlled amplifier. The circuit shown in FIG. 10 increases the output of the VCA exponentially with respect to the increase in the input (L + R) to the peak detector 520, but the output of the VCA is never less than the input of the peak detector 520. Absent. These outputs are supplied to an amplitude adjustment potentiometer 540,
From the output of the potentiometer 540, a dynamically boosted added signal component (L + R) is provided on a line 541.
b is generated, and this signal (L + R) b is supplied to the mixer together with the difference signal (LR) p which is servo-controlled and equalized in the addition amplifier 471 of FIG. When the system of FIG. 9 is used without using the directional servo circuit of FIGS. 3 and 4, the dynamically boosted supplemental sum signal is output from potentiometer 266 of the directional servo circuit of FIG. Instead, it is provided by the dynamically boosted sum signal of FIG.

When the system of FIG. 9 is used without using a directional servo circuit, the servo controlled and equalized difference signal component (LR) p is split and
(LR) and (RL) components are provided. The processed difference signal components (LR) p and (RL) p, and the dynamically boosted sum signal (L + R) p from line 541 in FIG. 10, are as shown in FIG. Supplied to the mixer. The processed difference signal (L-R) p from the summing amplifier 420 of FIG. It is supplied to the potentiometer 522. The processed difference signal (R−
L) p is combined with the boosted sum signal (L + R) b in summing amplifier 554, the output of which is provided to a second width adjustment potentiometer 556. The signals obtained from the wiper arms of the potentiometers 552, 556 are supplied to the mixer 560 together with the input signals Lin, Rin to provide mixer output signals Lout, Rout.

It will be appreciated from the foregoing that, in addition to servo controlled equalization by the separation band of the difference signal, the sum signal is dynamically boosted. That is, any signal in the sum signal is multiplied by the directional servo operation or the operation of the dynamic boost circuit of FIG.
Further, the addition signal is 552, 556 in FIG. 11 or 223 in FIG.
a, 223b is supplied via the combined width adjustment potentiometer, so that the increment of the sum signal component is directly controlled (along with the processed difference signal) according to the setting of the width control potentiometer. . Obviously, other configurations of the combined attenuator circuit, such as a combined voltage controlled attenuator, can be used in place of the various combined potentiometers described herein.

The main and unexpected benefit of using a multi-channel servo equalizer configuration (a configuration introduced to eliminate reverberation filters) is that this configuration allows independent control of the upper and lower frequency bands of the difference signal. Conventional systems once again consider maintaining the ratio of the processed difference signal to the sum signal. Thus, for example, when the summation signal increases only in the low frequency band, the system of our earlier patent provides a boost of the difference signal over the entire band that the system handles. Similarly, an increase in the upper component of the sum signal causes a boost of the difference signal over the full bandwidth of conventional systems. With the multi-channel configuration shown in FIG. 7, an increase in the summation signal that occurs only in the lower frequency band produces, for example, an associated boost of the difference signal in the corresponding lower band only. Thus, the fixed desired ratio of the difference signal and the sum signal is more accurately maintained for each band. That is, the circuit described herein maintains, if necessary, the desired fixed ratio of the processed difference signal and the summed signal independently for the upper band or lower band, and then the other components of these two bands. Is not inappropriately dispersed.

Yet another advantage of this multi-channel servo equalizer system is that there is no need to calibrate for any possible phase shift caused by the reverberation filters of conventional systems.

Thus, it will be appreciated that this configuration provides two separate and independent amplitude controls, or attenuation potentiometers, for the sum signal component provided through the directional servo circuit. The first of these damping controls is provided by potentiometer 202 of FIG. 3, and the second of these independent controls is of the fourth.
Provided by the potentiometer 266 shown. The attenuation of the added signal component in the system using the directional servo circuit can prevent the added signal from overwhelming the operation of the directional servo circuit. Such occupation is prevented because the primary function of the directional servo circuit is to enhance the difference signal component.

Before transmitting the combined signal through the directional servo circuit, a portion of the sum signal and a portion of the difference signal are mixed. Third and fourth
The configuration shown in the figure helps to solve the problem of apparent weakening of the center stage sound source, such as a single player, when using this directional servo circuit. The arrangement of FIGS. 3 and 4 provides at the output of potentiometer 266 a further dascinically enhanced summation signal, which is
At 240, 242, the directionally enhanced left and right input signals are combined. The embodiment shown in FIG. 12 provides this dynamically enhanced summation signal and uses a simplified circuit including a center voltage controlled amplifier to prevent the apparent weakening of the center stage signal. This is an embodiment of the present invention. The circuit of FIG. 12 is specifically configured to be used with the multi-band servo controlled equalizer configuration of FIG. 9, and further includes substantially all of the components of FIG. Components in FIG. 12 that are the same as components in FIG. 2 are designated by like reference numerals, and are preceded by the number 5. Therefore, the peak detector 560 of FIG. 12 corresponds to the peak detector 60 of FIG. 2, and the voltage control amplifier 58 of FIG.
0 corresponds to the voltage control amplifier 80 in FIG. 2, and the peak detector 660, the amplifier 666, and the voltage control amplifier 680 in FIG.
Respectively correspond to the peak detector 160, the amplifier 166, and the voltage control amplifier 180 in FIG. Certain components of FIG. 12 are preceded by the number 6 (instead of the number 5),
It depends on whether the reference number in the figure is 100 or more.
For example, the amplifier 680 in FIG. 12 corresponds to the amplifier 180 in FIG. In addition to the same components as in FIG. 2 (replicated in FIG. 12), FIG. 12 further includes a gain adjustment circuit 590, a center voltage control amplifier 592, an averaging circuit 594, and common mixers 596, 598.

The modified directional servo circuit shown in FIG. 12 receives the signal (LR) p from the summing amplifier 471 of FIG.
These signals are supplied to the voltage controlled amplifiers 580 and 680 directly and via the inverter 542. The output and input of the voltage controlled amplifier are compared in differential circuits 582 and 682, respectively, to provide feedback signals to non-inverting peak detectors 572 and 672, respectively. The output of this peak detector is
The input signals Lin and Rin are compared with the outputs of the peak detectors 560 and 660, respectively. This is amplifier 566 and 666
In addition, a controlled ratio input is provided via input resistance networks 562, 570 for amplifier 566, and
Resistor network 662, 670 for amplifier 666 input
Feed through. The ratio of the amplifier input resistance is the same as the value stated for the corresponding input resistance in FIG. The outputs of the amplifiers 566 and 666 are supplied as control signals to the voltage control amplifiers 580 and 680 of the left and right directional servo circuits, respectively. These two control signals, which appear at the outputs of amplifiers 566 and 666, are summed and divided by two by averaging circuit 594 to provide a control signal to a center or sum signal voltage control amplifier 592, which is Addition circuit 413 in FIG.
An input signal is received from a gain adjustment circuit 590 that provides a selected and fixed gain adjustment of the sum signal (L + R) obtained from. Therefore, the output of the central voltage control amplifier 592 is
In FIG. 12, it is identified as K (L + R). FIG. 5 is a variation of a dynamically enhanced summation signal that is provided to width adjustment potentiometers 523a and 523b with an associated wiper arm, which process and enhance the left and right channels. The output of the voltage control amplifiers 580 and 680 is received for the output signal. Several signals are combined in left and right mixers 596, 598, where mixer 596 includes a left channel input Lin, a left directional processed enhanced difference signal (LR) pe, and a dynamically enhanced sum signal. K (L + R) is bound. The right mixer 598 includes a right channel input Rin, a right channel processed and enhanced directional signal (RL) pe,
Combining the dynamically enhanced sum signal K (L + R) from potentiometer 523, the two mixers provide output signals Lout, Rout, respectively.

The arrangement of FIG. 12 differs from the arrangements of FIGS. 3 and 4 in that a portion of the summation signal is combined with the directional servo-controlled left and right channel signals to prevent a clear attenuation of the center stage sound. And are functionally identical. The summed signal is adjusted with respect to amplitude by potentiometer 523 at the same time as any adjustment of left and right channel potentiometers 523a and 523b, so that 3
All three components are adjusted simultaneously for adjustment of the stereo sound field width.

The mixer output of FIGS. 1, 4 and 11 can be supplied to a recording device instead of a speaker when the system is used for recording. This system can be used to make recordings that adapt to the augmented signal for playback on a conventional playback system as described in our earlier patent 4,748,669. Such a recording, when played back on a conventional playback device, produces a left and right stereo output signal, which is a modified version of the left and right input signal, having various enhanced components as described above.

While the configuration described for the embodiments is a desired configuration, digital configurations are also contemplated. For example, in the system shown in FIG. 7, a digital configuration can be applied to all or most of the circuits, or an analog circuit can be used for an audio signal and a digital technique can be applied to a control circuit.

The peak detector described and used in the above circuit is:
One of several common types of envelope detectors. Obviously, other types of envelope detectors can be used.

Continuation of front page (56) References Patent 2528154 (JP, B2)

Claims (21)

(57) [Claims] 1. A means for supplying an addition signal and a difference signal respectively indicating a sum and a difference between left and right input signals, and said addition signal according to an amplitude level of said difference signal within a plurality of selected frequency bands. Means for changing the amplitude level of the difference signal and supplying the processed addition signal and the difference signal; and changing the amplitude of the processed difference signal in accordance with a change in the amplitude of one of the left and right input signals. A first servo means (40) for providing an enhanced difference signal of one direction; and changing an amplitude of an inverted signal of the processed difference signal according to a change in the amplitude of the other of the left and right input signals; Second servo means (44) for providing an enhanced difference signal in a second direction
Means for providing left and right stereo output signals by amplifying and combining each of the left and right input signals, the processed sum signal, and the first and second directional enhanced difference signals with a predetermined gain. A stereo sound image enhancement system comprising: 2. The stereo audio image enhancement system according to claim 1, wherein an amplitude change of said processed difference signal is larger than an amplitude change of said one input signal. 3. The first servo means has a feedback loop (86, 72, 66) connected between the first directional enhanced difference signal and the one of the input signals. ,
The feedback loop of claim 1, wherein the feedback loop changes the amplitude level of the processed difference signal in response to the amplitude level of the first directional enhanced signal and the one input signal. Stereo sound image enhancement system. 4. The first servo means comprises means for generating a feedback signal (86) indicative of an amplitude difference between the first directional enhanced difference signal and the processed difference signal. The stereo sound image enhancement system according to claim 1, wherein: 5. The first servo means includes: means for providing a feedback signal indicative of a difference between the first directional enhanced difference signal and the processed difference signal; and the feedback signal. And a means (60, 66) for generating a control signal that is a function of the one of the input signals and an amplifier (80) for amplifying the processed difference signal. The stereo sound image enhancement system according to claim 1, wherein the system is determined by a signal. 6. The first servo means includes a first amplifier (80), the second servo means includes a second amplifier (180), and the first and second amplifiers include a control input and a signal input. Wherein the processed difference signal is connected to the signal input of the first amplifier, and the processed inverted difference signal is connected to the signal input of the second amplifier, the first and second Of the difference signal of the first and second directions
Output by an amplifier, and the first and second servo means respectively generate a feedback signal (82, 182) indicating a difference between input and output signals of the corresponding amplifier, and correspond to each of the feedback signals. The first and second signals are compared with a stereo input signal.
2. The stereo system according to claim 1, further comprising means for providing a control signal, wherein the first and second control signals are respectively connected to the corresponding first and second amplifiers. Audio image enhancement system. 7. A means (411, 413) for providing an addition signal and a difference signal indicating a sum and a difference between left and right stereo input signals, and a means for attenuating a low frequency component of the difference signal to generate a high frequency difference signal. A first filter means (472), a second filter means (450) for attenuating a high frequency component of the difference signal to generate a low frequency difference signal, and an amplitude of the high frequency difference signal component, First means (47) for providing a high frequency boost difference signal by boosting from the amplitude in the corresponding frequency band.
Second means for providing a low frequency boost difference signal by boosting the amplitude of the low frequency difference signal component from the amplitude of the added signal component in the corresponding frequency band. (45
2, 454, 460, 462); combining means (471, 550, 554, 56) for combining the high frequency and low frequency boost difference signals with the sum signal and the left and right stereo input signals to provide left and right stereo output signals.
0) and a stereo audio image enhancement system comprising: 8. The high frequency and low frequency difference signal components are separated from each other by an intermediate frequency bandwidth, and the difference signal components in the intermediate frequency bandwidth are the high frequency and low frequency boost difference signals and the sum signal. 8. The stereo audio image enhancement system according to claim 7, wherein the left and right output signals are combined to generate the left and right output signals. 9. A low-bandpass filter (462) for supplying a low-frequency addition signal component in response to the addition signal, the second means comprising: a low-frequency difference signal component and the low-frequency addition signal component; Means for maintaining a predetermined amplitude ratio (454, 46
The stereo audio image enhancement system according to claim 7, comprising: (4, 460). 10. The means for maintaining the predetermined ratio comprises means for maintaining the amplitude of the low frequency difference signal component at a value greater than or equal to the amplitude of the low frequency addition signal component. 10. The stereo sound image enhancement system according to item 9. 11. The stereo audio image enhancement system according to claim 9, wherein said predetermined ratio is a value between 1: 1 and 3: 1. 12. The low frequency difference signal component comprising: a voltage control amplifier (452) for providing a boosted low frequency difference signal component in response to the low frequency difference signal component; Means (459) for supplying a control signal in response to the low frequency addition signal component, and means (45) for controlling the gain of the voltage control amplifier according to the control signal.
The stereo audio image enhancement system according to claim 9, comprising: (7). 13. An operation amplifier (459) having an output for generating said control signal and a first input, and an amplitude of said low frequency difference signal component and said low frequency signal at said first input. 13. The stereo sound image enhancement system according to claim 12, further comprising means (465, 467) for supplying a signal indicating a predetermined ratio of the amplitude of the added signal component. 14. The combination of claim 7 wherein said combining means includes means (471) for combining said high and low frequency boost difference signals and said difference signal to generate a processed difference signal. Stereo sound image enhancement system. 15. Servo means (440, 44) for changing the amplitude of the processed difference signal in response to a change in the amplitude of one of the input signals, and providing a directionally enhanced difference signal.
4) wherein the amplitude change of the input signal is detected by a first peak detector (60, 160) and the corresponding amplitude change of the processed difference signal is detected by a second peak detector (72, 17).
Means (550, 554, 560) for detecting left and right directions by combining the enhanced directional difference signal, the sum signal, and the input signal to provide left and right stereo output signals. 15. The stereo sound image enhancement system according to claim 14, comprising: 16. A means for providing an addition signal and a difference signal indicating a sum and a difference of left and right stereo input signals, respectively.
First equalizer means (450, 452, 454, 460, 462, 464) for adjusting the amplitude level of said difference signal in a first frequency band to generate a first modified difference signal; One equalizer means for providing an adjustment level of the difference signal in the first frequency band that is dependent on an amplitude level of the first modified difference signal and the sum signal; and an amplitude of the difference signal in a second frequency band. Second equalizer means (472, 474, 478, 484, 490, 488) for adjusting the level to produce a second modified difference signal, wherein said second equalizer means comprises a second equalizer means for adjusting said level in said second frequency band. Providing a second modified difference signal and an adjustment level of the difference signal that is dependent on an amplitude level of the sum signal, wherein the difference signal and the low-pass processed difference signal and the high-pass processed difference signal component are provided. Combined and provides a composite processed difference signal That coupling means and (471), dynamic enhanced sum signal generating means for generating a sum signal augmented dynamically by boosting only variable amount the amplitude level of the sum signal (520,522,530,5
34) wherein the variable amount is determined by a feedback loop that compares the level of the summation signal and the dynamically enhanced summation signal to generate the dynamically enhanced summation signal, and Means for providing left and right enhanced stereo output signals by combining the difference signal, the dynamically enhanced sum signal, and the input signal (55).
0, 554, 560), and a stereo audio image enhancement system. 17. The dynamic enhancement addition signal generating means includes: a first input to which the addition signal is connected, a second input to which a control input is connected, and an output for providing the dynamically enhanced addition signal. And a voltage control amplifier (530) for amplifying the sum signal, wherein the control signal includes an amplitude of the dynamically enhanced sum signal generated at an output of the voltage control amplifier and the first control signal.
17. The stereo audio image enhancement system according to claim 16, wherein the system is generated by comparing an amplitude of the sum signal provided to an input, and a gain of the voltage control amplifier corresponds to the control signal. 18. The dynamic enhancement addition signal generating means combines the composite processed difference signal and the addition signal,
Combining means (208, 210) for providing a combined signal; and an amplifier (80, 180) for inputting the combined signal, for boosting the amplitude level of the combined signal to enhance directionality. Servo means (40, 4) for providing a directional enhanced combined signal having a summed signal and a difference signal component.
4) wherein the amplifier supplies a boost amount dependent on the level of one of the input signal, the combined signal and the directional enhanced combined signal to the combined signal;
The directional enhanced combined signal changes in response to a corresponding change in the one input signal, separating the directional enhanced summed signal component from the combined signal and the dynamically enhanced combined signal component. 17. The stereo sound image enhancement system according to claim 16, further comprising: means (250, 244, 264) for generating the added signal. 19. The means for generating the dynamically enhanced sum signal has a first input connected to the sum signal and a first output for providing the dynamically enhanced sum signal. A central voltage control amplifier (592) for boosting the addition signal to generate the dynamically enhanced addition signal, and a means (560, 566, 660, 666) and means (594) for combining the left and right control signals to provide a combined control signal, wherein the gain of the central voltage control amplifier is equal to the combined control signal. 17. The stereo sound image enhancement system according to claim 16, wherein the stereo sound image enhancement system changes according to the condition. 20. A method for performing stereo sound recording from left and right stereo sound source signals so as to generate enhanced left and right stereo output signals of a stereo sound image when reproduced by an audio reproduction device, Adding a sound source signal to generate an addition signal; subtracting the right stereo sound source signal from the left stereo sound source signal to generate a difference signal; and selecting a difference signal in a selected first frequency band including a frequency lower than a center frequency band. Boosting the first component set by giving directionality to the first component set of the difference signal using an amplifier; and selecting a second frequency band including a frequency higher than the center frequency band. The second component set of the difference signal at step (b) is given a direction by using an amplifier, so that the second component set Providing a processed difference signal by combining the boosted high and low frequency difference signal components with the difference signal having a frequency band intermediate the first and second frequency bands. Combining the summed signal with the processed difference signal and the stereo sound source signal to provide an enhanced left and right stereo output signal of the stereo audio image; and enhancing the stereo audio image. Supplying a left and right stereo output signal to the audio recording device; and activating the audio recording device to perform the stereo audio recording. 21. Enhancement of the processed difference signal by amplifying the amplitude of the processed difference signal as a function of the amplitude change of the left sound source signal, thereby providing a directional enhanced left signal. Providing a directional enhanced right signal by enhancing and inverting the processed difference signal as a function of the amplitude change of the right sound source signal;
Combining the directional enhanced left and right signals and the sum signal to provide the enhanced left and right stereo output signals. Method.